The present invention relates to an ultrasonic transducer array and a method of manufacturing the same.
In our co-pending application number 9116478 there is disclosed an ultrasonic transducer array for use in visualising the internal organs of the human body, for example in a system as disclosed in our UK Patents 2,212,267 and 2,233,094. As explained in our earlier co-pending application number 9116478 there are considerable problems to overcome in manufacturing such a transducer array because of its extremely small size.
A method of manufacture disclosed in our above mentioned co-pending application number 9116478 gives a high performance ultrasonic transducer but it is relatively expensive to manufacture. There are other advantages to this method of manufacture, relating to i) the ability to have well-designed acoustic layers, ii) the removal of the need to have a rigid (tungsten carbide) support and iii) the concomitant increase in backing layer thickness.
According to a first aspect of the present invention in a method of manufacturing an ultrasonic transducer array a plurality of discrete ceramic transducer elements are formed on an initially flat flexible substrate together with electrically conductive tracks, through which the transducer elements will be energised in use, the flexible substrate with the discrete transducer elements and conductive tracks mounted thereon then being formed into a cylinder, the substrate being radially outwardly of the transducer elements.
According to a second aspect of the present invention the substrate comprises at least two laminae, a first lamina being flexible and acting as the second part of a two layer matching layer and having the conductive tracks thereon and a second lamina being sandwiched between said first lamina and said transducer elements which are carried thereon, the second lamina having a higher acoustic impedance than the first lamina and acting as the first part of the two layer matching layer.
According to a third aspect of the present invention the first lamina is in the form of a film which is deposited on the flexible substrate.
According to a fourth aspect of the present invention the flat assembly comprising the substrate, the transducer array and the conductive tracks is shaped into a cylinder by means of a mould. The mould may comprise two semi-circular cross-section mould elements to which suction may be applied to draw the flat assembly into the mould in order to make it confirm to the shape of the inside of the mould elements.
According to a fifth aspect of the present invention the flat assembly comprising the substrate, the transducer array and the conductive tracks is then drawn through a guide member constructed so that the flat assembly is progressively shaped into a cylinder.
According to a sixth aspect of the present invention a multiplexing circuit is provided on the flexible substrate.
According to a seventh aspect of the invention the multiplexing circuit includes an integrated circuit which is flip-chip bonded in position.
According to an eighth aspect of the present invention the multiplexing circuit is made up of a plurality of individual integrated circuits arranged in a polygonal configuration.
According to a ninth aspect of the present invention the polygon comprises a square.
According to a tenth aspect of the present invention there is an annular space between the assembled circular transducer array and the distal end of the catheter, this gap being filled with a material which acts both as an adhesive and as an acoustic backing layer.
According to an eleventh aspect of the present invention an earth return on the top of the pies-electric transducer is electrically connected to an earth return on the bottom of the substrate to thereby form a common return.